1. Field of the Invention
The present invention relates to an alert display device and an alert display method which display a display image for highlighting an object to be alerted in an actual scene in front of a driver of a vehicle or around the vehicle in a superimposing manner.
2. Related Background Art
A variety of devices which support a driver have been developed, and of these devices, a device which provides information regarding an object to be alerted, such as a pedestrian, in front of the driver or around the driver is known. In order to inform the driver of the presence of an object to be alerted, an object to be alerted is detected using various sensors, such as a radar sensor, and the detected object to be alerted is highlighted. For example, Japanese Unexamined Patent Application Publication No. 2012-218505 describes a vehicular display device (for example, a night view device) which displays a highlight image for highlighting an object to be detected (for example, a pedestrian) in a frontward image obtained by imaging the front of a vehicle in a superimposing manner, and enlarges the size of the highlight image with respect to a reference size corresponding to size information with an increase in the traveling speed of the vehicle.
Japanese Unexamined Patent Application Publication No. 2011-119917 is another example of the related art.
As a device which highlights an object to be alerted, a head-up display (HUD) which highlights an object to be alerted in an actual scene in front of a driver or around the driver (for example, displays a frame surrounding the object to be alerted or an underscore below the object to be alerted in a superimposing manner) is known. In case of the head-up display, a frame or the like is imaged on the front side of a front glass for an actual scene which is actually viewed by the driver, instead of an image. The position of the frame or the like on the imaging surface (the position where the frame or the like is projected on the front glass) is determined from the detection position of the object to be alerted detected by the sensor. The sensor has a detection error. For this reason, if the detection position of the object to be alerted is deviated from the actual position of the object to be alerted due to the detection error, the frame or the like displayed on the imaging surface in a superimposing manner may be deviated from the object to be alerted in the actual scene. The position of the eyes of the driver changes depending on the seated height, driving posture, or the like of the driver, and the angle at which the driver looks at the object to be alerted changes depending on the position of the eyes of the driver. For this reason, the display image, such as the frame, displayed on the imaging surface in a superimposing manner may be deviated from the object to be alerted. For example, in an example shown in FIG. 6, when a pedestrian W is present as an object to be alerted on the front side, if the eyes of the driver who looks at the pedestrian W are at the position indicated by reference numeral E1, the position on an imaging surface S of the head-up display becomes the position indicated by reference numeral S1, and if the eyes of the driver who looks at the pedestrian W are at the position indicated by reference numeral E2, the position on the imaging surface S becomes the position indicated by reference numeral S2. In this way, since the angle at which the driver looks at the pedestrian W changes depending on the position of the eyes of the driver, and the position on the imaging surface S changes, the pedestrian W may protrude from the display image, such as the frame, displayed on the imaging surface S in a superimposing manner.
Accordingly, an object of the invention is to provide an alert display device and an alert display method which suppress deviation of a display image displayed on an object to be alerted in an actual scene in a superimposing manner.
According to an aspect of the invention, there is provided an alert display device which displays a display image for highlighting an object to be alerted in an actual scene in front of a driver of a vehicle or around the vehicle in a superimposing manner, the device including a detection unit configured to detect the object to be alerted in front of the vehicle or around the vehicle, a control unit configured to perform display control for positioning the display image conforming to the position of the object to be alerted detected by the detection unit, and a display unit configured to display the display image for highlighting the object to be alerted detected by the detection unit in the actual scene in front of the driver of the vehicle or around the vehicle based on the display control of the control unit, in which the control unit adjusts the size of the display image based on the position of the object to be alerted detected by the detection unit and/or a range in which the eyes of the driver are likely to be present.
In this alert display device, the object to be alerted which is in front of the vehicle or around the vehicle and to which the driver should be alerted is detected by the detection unit. In the alert display device, the display image is displayed on the display unit in a superimposing manner to highlight the object to be alerted in the actual scene in front of the driver of the vehicle or around the vehicle by the display control of the control unit. In particular, the control unit adjusts the size of the display image based on the position of the object to be alerted or the range in which the eyes of the driver are likely to be present. The detection unit has a detection error. For this reason, the position of the object to be alerted detected by the detection unit includes an error, and the range of the detection error changes depending on the position of the object to be alerted. However, the size of the display image is adjusted according to the position of the object to be alerted, whereby, even if the detection position of the object to be alerted detected by the detection unit is deviated from the actual position due to the detection error, the display image which is of size in consideration of the amount of deviation can be displayed. The position of the eyes of the driver changes depending on the seated height, driving posture, or the like of the driver. However, the size of the display image is adjusted according to the range in which the eyes of the driver are likely to be present, whereby, even if the position of the eyes of the individual driver changes, the display image which is of size in consideration of the difference in the position of the eyes can be displayed. Accordingly, even if the display position in the superimposition display is deviated from the position of the object to be alerted in the actual scene depending on the position of the object to be alerted (the detection error of the detection unit) or the position of the eyes of the driver, the object to be alerted is not significantly deviated from the display range of the display image of adjusted size, and the object to be alerted can be appropriately highlighted by the display image. In this way, the alert display device adjusts the size of the display image displayed in a superimposing manner based on the position of the object to be alerted and/or the range in which the eyes of the driver are likely to be present, whereby it is possible to suppress deviation of the display image displayed in a superimposing manner with respect to the object to be alerted in the actual scene.
The actual scene is a scene which is actually viewed from the driver in front of the vehicle or around the vehicle. The object to be alerted is an object to which the driver should pay attention when driving the vehicle among objects in the actual scene in front of the vehicle or around the vehicle, and is an object to which the driver needs to be alerted. The superimposition display is one display form of highlighting. Highlighting is display which highlights the object to be alerted in the actual scene, and displays the display image which highlights the object to be alerted. In particular, the superimposition display is display in which the display image is positioned conforming to the position of the object to be alerted in the actual scene when viewed from the driver. As the display image to be displayed in a superimposing manner, for example, a display image of a frame which is displayed to surround the object to be alerted in the actual scene, or a display image of an underscore which is displayed below the object to be alerted in the actual scene is used.
In the above-described alert display device, the control unit may adjust the size of the display image based on an error range of the detection unit according to the position of the object to be alerted detected by the detection unit. The error range of the detection unit changes depending on the position of the object to be alerted. For this reason, the error range of the detection unit according to the position of the object to be alerted is determined, and the size of the display image is adjusted based on the error range. In this way, the size of the display image is adjusted according to the error range of the detection unit, whereby, even if the detection position of the object to be alerted is deviated from the actual position due to the detection error of the detection unit, superimposition display can be performed by a display image which is of size in consideration of the amount of deviation.
In the above-described alert display device, when the position of the object to be alerted detected by the detection unit is far from the vehicle, the control unit may increase the error range of the detection unit and may increase the size of the display image compared to a case where the position of the object to be alerted is close to the vehicle. Accordingly, if the position of the object to be alerted is far from the vehicle (detection unit), while the error range of the detection unit increases, and the detection position of the object to be alerted may be significantly deviated from the actual position, superimposition display can be performed by a display image which is of size in consideration of the amount of deviation.
In the above-described alert display device of the invention, the control unit may adjust the size of the display image based on the size of the object to be alerted detected by the detection unit. Accordingly, even if the object to be alerted is a large object, superimposition display can be performed by a display image which is of size in consideration of the size of the object.
In the above-described alert display device, the display unit may be a head-up display which is mounted in the vehicle.
According to another aspect of the invention, there is provided an alert display method which displays a display image for highlighting an object to be alerted in an actual scene in front of a driver of a vehicle or around the vehicle in a superimposing manner, the method including a detection step of detecting the object to be alerted in front of the vehicle or around the vehicle, a control step of performing display control for positioning the display image conforming to the position of the object to be alerted detected in the detection step, and a display step of displaying the display image for highlighting the object to be alerted detected in the detection step in the actual scene in front of the driver of the vehicle or around the vehicle based on the display control in the control step, in which, in the control step, the size of the display image is adjusted based on the position of the object to be alerted detected in the detection step and/or a range in which the eyes of the driver are likely to be present. The alert display method acts in the same manner and has the same effects as the above-described alert display device.
According to the invention, the size of the display image displayed in a superimposing manner is adjusted based on the position of the object to be alerted or/and the range in which the eyes of the driver are likely to be present, whereby it is possible to suppress deviation of the display image displayed in a superimposing manner with respect to the object to be alerted in the actual scene.